KR20050046609A - Semiconductor laser device and manufacturing method for the same - Google Patents

Abstract

A semiconductor laser device comprising a substrate 101 and two or more active layers 103 and 106, wherein two resonators 201 and 204 having the active layers 103 and 106 are disposed in parallel with each other, In addition, the resonators 201 and 204 have different lengths in regions where currents of the active layers 103 and 106 are injected. Accordingly, in the two-wavelength laser, the length of the effective resonators 201 and 204 of a plurality of lasers having different characteristics such as an infrared laser and a red laser is independently exceeded by the limitation of the resonator length determined by cleavage. It becomes possible to design and manufacture, and to provide the semiconductor which improved each laser characteristic by employing the resonator length suitable for a desired characteristic, respectively.

Description

Semiconductor laser device and manufacturing method therefor {SEMICONDUCTOR LASER DEVICE AND MANUFACTURING METHOD FOR THE SAME}

The present invention relates to digital versatile disk random access memory (DVD-RAM), digital versatile disk recordable (DVD-R), digital versatile disk rewritable (DVD-RW), DVD + R, DVD + RW, and compact disk recordable (CD-R). ), CD-RW, DVD-ROM (digital versatile disk read only memory), CD-ROM, DVD-Video and CD-DA such as optical disk devices or semiconductor lasers for optical information processing, optical communication, optical measurement, etc. An apparatus and a method of manufacturing the same.

AlGaInP-based red lasers having a wavelength of 650 nm are used for reading and writing pick-up light sources such as DVD-RAM. On the other hand, an AlGaAs infrared laser having a wavelength of 780 nm is used as a pick-up light source for reading and writing CD-R or the like. In order to cope with these two disks, one drive requires both red and infrared lasers. For this reason, drives having two optical integration units for DVD and CD are generally spreading.

However, two-wavelength lasers in which two lasers are integrated on the same substrate have been put to practical use in order to cope with a single optical integration unit in response to recent miniaturization, low cost, and simplification of an optical system assembly process. As a conventional example of such a two-wavelength laser, Japanese Laid-Open Patent Publication No. 2000-11417 is mentioned. This is a monolithic integration of a 650nm AlGaInP-based red laser and a 780nm AlGaAs-based infrared laser on a GaAs substrate, which includes both lasers for DVD / CD on one optical integration unit. We suggest optical pickup.

The two-wavelength laser, like the conventional laser, forms a resonator by cleavage. Since the resonator length is determined by cleavage positions at both ends, the resonator lengths of the red laser and the infrared laser are necessarily the same. The resonator length is one of parameters that determine laser characteristics such as maximum light output, oscillation threshold current, and efficiency. However, in the case of a two-wavelength laser, there is a limitation that the resonator length cannot be optimized independently of the red laser and the infrared laser.

For example, in a laser in which a high power red laser and a high power infrared laser are monolithically integrated, when a high power of 200 mW is to be realized by a red laser, the resonator length is practically at least 900 µm or more. However, when the resonator length of the infrared laser is 900 µm or more, the operating current is greatly increased as compared with the conventional laser, and there is a concern that adverse effects such as increase in power consumption and acceleration of element deterioration due to heat generation are feared. From this situation, there is a possibility that the high power of the two-wavelength laser becomes difficult.

The semiconductor device of the present invention is a semiconductor laser device including a substrate and two or more active layers, wherein two resonators each having the active layer are arranged in parallel with each other, and in a region into which a current of the active layer is injected. The resonator is characterized in that the length is different.

In the method of manufacturing a semiconductor device of the present invention, a step of forming a first laminated structure by sequentially laminating a first first conductive cladding layer, a first active layer, and a first second conductive cladding layer on a substrate. and,

Removing the first laminated structure in a predetermined region on the substrate;

Forming a second laminated structure by sequentially laminating a second first conductive clad layer, a second active layer, and a second second conductive clad layer on the substrate including the first laminated structure; and,

Removing the second laminated structure formed on the first laminated structure;

Forming a layer serving as an impurity diffusion source in a predetermined region on the first laminated structure and the second laminated structure;

Heat-treating the substrate to diffuse impurities from the layer serving as the impurity diffusion source to the first stacked structure immediately below and the second stacked structure, so that at least one of the first active layer or the second active layer Including the process of disordering any part,

A region in which the impurity is diffused in the first laminated structure and a region in which the impurity is diffused in the second laminated structure are different in width in the resonator direction.

The two-wavelength laser according to the present invention contributes to an effective resonator length, that is, laser oscillation, by employing a structure that prevents the injection of current into the active layer in a part of a region from one or both laser sections toward the center of the resonator. It is possible to independently control the length of the active layer in the resonator direction. As a result, setting of an optimal resonator length for each of the red and infrared lasers is realized, and the laser characteristics can be improved.

In the present invention, when the length of the resonator in the region into which the current of the active layer is injected is 1000 μm for the red laser and 700 μm for the infrared laser, devices having desired operating current, light output, and temperature characteristics can be realized. have.

In the present invention, the "two resonators are parallel to each other" is preferably parallel within a range of ± 1 degree or less.

It is preferable that the said at least one active layer is comprised by a quantum well. The quantum well has the same effect as the conventional laser, which reduces the operating current density by increasing the luminous efficiency with respect to the injection carrier. In addition, the quantum well structure allows the band gap due to crystal disorder in the case of Zn diffusion. Since enlargement occurs, if this is applied to the non-gain region (region where no current is injected) of the element having the shorter effective resonator length, it is possible to prevent deterioration of characteristics such as an increase in operating current due to absorption of light.

In some regions of the at least one resonator toward one side of the resonator toward the center of the resonator, a region in which no current is injected into the active layer is formed, and the length of the region is different between the two resonators so that the active layer It is preferable that the lengths of the resonator directions of the region into which the current is injected are different from each other. Because the red laser has a weaker carrier confinement and a higher thermal resistance than the infrared laser, the light output limit due to heat saturation is low. Therefore, by increasing the resonator length, the red laser reduces the cross-sectional reflectance, improves heat dissipation, and improves temperature characteristics. Needs to be. On the other hand, when the infrared laser is lengthened to the resonator length equivalent to that of the red laser, the operating area is greatly increased as compared with the conventional single laser by increasing the light emitting area.

It is preferable that the band gap energy of the semiconductor layer in the region where propagation light exists in the region where no current is injected into the active layer is greater than the energy of the emission wavelength of the active layer. This is because when the band gap of the region is smaller than the energy of the emission wavelength of the active layer, absorption of light occurs to cause deterioration of characteristics such as a threshold current, an increase in operating current, and a decrease in light output.

The two active layers each include (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 ≦ _y ≦ 1) and Al _z Ga _lz As (0 ≦ _z ≦ 1). It is preferable that the wavelengths obtained from two active layers are 630 nm or more and 690 nm or less, and 760 nm or more and 810 nm or less, respectively. This is because the laser light in the wavelength band is required for data writing and writing of the DVD optical disc and the CD optical disc, respectively.

It is preferable that each maximum light output in one cross section obtained by the two active layers is 80 mW or more. The above is the optical output required for writing data on the optical disk at about twice the speed or more.

The band gap of at least a portion of the region of the quantum well active layer in one or both cross-sections of the at least one resonator facing the resonator center direction is enlarged by disordered by impurity diffusion or impurity implantation, so that no current is injected. It is preferable that the length of the cross section of the resonator center from the end face having the blocking layer or the semiconductor layer or the electrode corresponding to the current injection path being removed and performing the above steps is different in the two resonators. By adopting such a manufacturing method, it is possible to precisely control the light emitting cross-sectional position spacing, and it becomes possible to form elements having optimal resonator lengths, respectively.

The at least two active layers are each composed of a layer including (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 ≦ _y ≦ 1), and the maximum light output of the two active layers It is preferable that the light output in this higher element is 50 mW or more, and the operation current of the element with the lowest maximum light output is 35 mA or less in light output 2 mW or more. By using one element as a high output laser capable of writing to a disk and the other as a low output laser capable of reading a disc at low operating current, the disk writing and reading are performed by a single high output laser, and from a conventional optical disk apparatus, Since the power consumption at the time of data reading can be reduced, development to products, such as a portable DVD, becomes easier.

According to the present invention, since it is possible to independently design and manufacture the effective resonator length of many lasers having different characteristics such as infrared laser and red laser, beyond the limitation of the resonator length determined by cleavage in the two-wavelength laser. By employing the resonator lengths suitable for the desired characteristics, the respective laser characteristics can be improved.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described.

(Embodiment 1)

1A to 2C and FIG. 2 each show a two-wavelength high-power laser having a light output of 200 mW class according to Embodiment 1 of the present invention. FIG. 1A is a plan view of the same and FIG. 1B is a sectional view taken along line I-I of FIG. 1A. 1C is a cross-sectional view taken along the line II-II of FIG. 1A and FIG. 2 is a perspective view thereof. Like numerals denote like materials or parts.

3A to 4D, and Figs. 4A to 4B and Figs. 5A to 5D are cross-sectional views showing the semiconductor laser manufacturing process according to the first embodiment of the present invention (however, Figs. 4A 'and 4B' are plan views). Here, it demonstrates according to the manufacturing process of FIGS.

(1) As shown in FIG. 3A, the infrared laser n-type cladding layer 102, the infrared laser active layer 103, and the infrared laser p-type cladding layer 104 are sequentially stacked on the n-type GaAs substrate 101. do. The infrared laser active layer 103 is constituted by a quantum well structure.

(2) As shown in FIG. 3B, in some regions including the red laser region, the infrared laser n-type cladding layer 102, the infrared laser active layer 103, and the infrared laser p-type cladding layer 104 are removed. do.

(3) As shown in Fig. 3C, the red laser n-type cladding layer 105, the red laser active layer 106, and the red laser p-type cladding layer 107 are sequentially stacked. The red laser active layer 106 is constituted by a quantum well structure.

(4) As shown in FIG. 3D, in some regions including the infrared laser region, the red laser n-type cladding layer 105, the red laser active layer 106, and the red laser p-type cladding layer 107 are removed. do.

(5) As shown in Fig. 4A, from both cross sections of the red laser p-type cladding layer 107 to an area of 10 m and from a cross section of the infrared laser p-type cladding layer 104, respectively, 10 m and 310 m, respectively. The zinc oxide film 301 is formed to the area.

(6) As shown in Fig. 4B, by heating, Zn is diffused into the active layer immediately below each of the regions 202, 203, 205, and 206 where the zinc oxide film is formed. By this process, the band gap is enlarged by disordering the hetero junctions of the quantum well layer and the adjacent barrier layer forming the active layer. This region is transparent to the wavelength emitted from the active layer. After heating, the zinc oxide film is removed. The lengths of the regions 201 and 204 are 680 µm and 980 µm, respectively.

(7) As shown in FIG. 5A, a part of the infrared laser p clad layer 104 and the red laser p clad layer 107 are etched to form a stripe mesa structure, respectively. The mesa has a width of 1 μm at the top and 3 μm at the bottom.

(8) As shown in FIG. 5B, the selective regrowth of the current block layer 108 is performed.

(9) As shown in Fig. 5C, the contact layer 109 is regrown.

(10) As shown in Fig. 5D, element separation is performed by etching the vicinity of the boundary between the infrared laser and the red laser to the substrate 101. The p-side electrodes 110 and 111 are formed on the region excluding 202 and 203 on the infrared laser and on the region 205 and 206 on the red laser, respectively. In addition, the n-side electrode 112 is deposited under the substrate to form a device.

In addition, the material, conductivity type, film thickness, and carrier concentration of each layer are shown in Table 1 below.

TABLE 1

A feature of the present invention is that the length of the resonator direction of the current injection region 201 of the infrared laser and the current injection region 204 of the red laser are different.

In the case of the conventional two-wavelength laser, the resonator lengths of the infrared laser and the red laser are the same. Fig. 6 shows the current-light output characteristics of the red laser and the infrared laser of the two-wavelength laser having any resonator length of 700 µm. The red laser cannot achieve the desired light output because of thermal saturation near 180mW. In order to obtain a light output of 200 mW or more, it is necessary to lengthen the resonator length of the red laser.

On the other hand, Fig. 7 shows current-light output characteristics of the red laser and the infrared laser of the two-wavelength laser having any resonator length of 1000 mu m. Although both the infrared laser and the red laser have obtained light output of 200 mW or more, the operating current of the infrared laser increases with the increase of the active layer volume compared with the laser having a resonator length of 700 µm. Due to this increase in power consumption, the battery operating time at the time of mounting on a portable device by battery driving becomes shorter than a device using a single laser.

In this embodiment, the effective resonator length of each of an infrared laser and a red laser is 680 micrometers and 980 micrometers, respectively. In the infrared laser, the actual resonator length is 1000 µm. An area where no current is injected is provided at 310 µm from the cross-section and 10 µm from the other cross-section, and the region does not contribute to light emission and further disorders the quantum well active layer. By enlarging the band gap, no waveguide loss due to light absorption occurs. As a result, as shown in Fig. 8, while the light output of the red laser achieves 200 mW, the operating current of the infrared laser exhibits a value comparable to that of the element having a resonator length of 700 m. In addition, the red laser also forms a current non-injection region and an active layer disordered region of 10 mu m in both cross sections, which are formed to avoid optical breakage due to light absorption in the cross section.

(Embodiment 2)

9A is a plan view of a high power / low power integrated red laser in accordance with Embodiment 2 of the present invention, FIG. 9B is a sectional view taken along line III-III of FIG. 9A, and FIG. 9C is a sectional view taken along line IV-IV of FIG. 9A.

10A to 10E are cross-sectional structural diagrams illustrating the process of manufacturing the semiconductor laser in Embodiment 2 of the present invention. Here, it demonstrates according to the manufacturing process of FIG. 10A-E.

(1) As shown in FIG. 10A, the n-type cladding layer 402 for the low power laser, the active layer 403, and the p-type cladding layer 404 are sequentially stacked on the n-type GaAs substrate 401. The active layer 403 has a quantum well structure. In the present embodiment, the n-type cladding layer 405, the active layer 406, and the p-type cladding layer 407 of the high power laser also serve as the respective layers.

(2) As shown in Fig. 10B, portions of the p-type cladding layers 404 and 407 are etched to form ridge waveguides.

(3) As shown in Fig. 10C, portions of the p-type cladding layers 404 and 407 are further etched to the substrate 401, and element separation of the low output laser and the high output laser is performed. In this embodiment, the resonator width is made smaller than that of the high output laser in order to reduce the operating current of the low output laser.

(4) As shown in FIG. 10D, Zn diffusion is performed to the active layer immediately below the regions indicated by 502, 503, 505, and 506 in FIG. The lengths of the regions 501 and 504 in Fig. 9 are 480 mu m and 980 mu m, respectively.

(5) As shown in FIG. 10E, the p-side electrode 408 and the n-side electrode 409 are formed.

 11 shows the current-light output characteristics of this device. While a high output laser realizes light output exceeding 200 mW, a low output laser realizes a light output of 10 mW required for reading with a low operating current of about 20 mA.

Since the conventional high output red laser for write DVD has a long resonator length, the operating current at the time of low output operation for data reading becomes high compared with the low output red laser with short read-only resonator length. However, as shown in this embodiment, two red lasers having different effective resonator lengths are monolithically integrated, and data writing is performed by a high power laser having a long resonator length and data reading by a low power laser having a short resonator length. It is possible to realize an optical pick-up that consumes less power than conventionally in reading data without degrading the performance of data writing.

As described above, the present invention is not limited to two-wavelength lasers, but can also be applied to monolithic integration of lasers of the same wavelength band.

According to the present invention, since it is possible to independently design and manufacture the effective resonator length of many lasers having different characteristics such as infrared laser and red laser, beyond the limitation of the resonator length determined by cleavage in the two-wavelength laser. By employing the resonator lengths suitable for the desired characteristics, the respective laser characteristics can be improved.

1A is a sectional view of a two-wavelength laser in the first exemplary embodiment of the present invention;

FIG. 1B is a cross-sectional view taken along line II of FIG. 1A;

1C is a cross-sectional view taken along the line II-II of FIG. 1A;

2 is a perspective view of a two-wavelength laser according to the first embodiment of the present invention;

3A-D are cross-sectional views of the manufacturing steps of the two-wavelength laser according to the first embodiment of the present invention;

4A-B are cross-sectional views of the production steps of the two-wavelength laser according to the first embodiment of the present invention;

4a '-b' is a plan view of the same,

5A-D are cross-sectional views of the manufacturing steps of the two-wavelength laser according to the first embodiment of the present invention;

6 is a current-light output characteristic diagram of a two-wavelength laser having a resonator length of 700 μm,

7 is a current-light output characteristic diagram of a two-wavelength laser having a resonator length of 1000 μm,

8 is a diagram showing current-light output characteristics of a two-wavelength laser according to the first embodiment of the present invention;

9A is a plan view of a high power and low power red laser monolithic integrated chip according to Embodiment 2 of the present invention;

9B is a cross-sectional view taken along line III-III of a,

9C is a cross-sectional view taken along line IV-IV of a;

10A-E are sectional views of the manufacturing process of the high power and low power red laser monolithic integrated chip according to the second embodiment of the present invention;

Fig. 11 is a current-light output characteristic diagram of a two-wavelength laser in the second exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

101: substrate 102: infrared laser n-type cladding layer

103: infrared laser active layer 104: infrared laser p-type cladding layer

105: red laser n-type cladding layer 106: red laser active layer

107: red laser p-type cladding layer 108: current block layer

109: contact layer 110, 111: p-side electrode

112: n-side electrode 201: current injection region of the infrared laser

204: current injection region of the red laser

Claims (17)

In a semiconductor laser device comprising a substrate and two or more active layers, Each of the two resonators having the active layer is arranged in parallel with each other, Further, the semiconductor laser device, characterized in that the length of the resonator in the region in which the current of the active layer is injected. The method of claim 1, The semiconductor laser device of which the light emission wavelength obtained by the said at least 2 said active layer differs, respectively. 3. The semiconductor laser device according to claim 2, wherein said at least one active layer is constituted by a quantum well. According to claim 1, wherein the end of the two resonators in the longitudinal direction of the cross section is present, In some regions of the at least one resonator toward the center of the resonator in one or both cross sections, a region in which no current is injected into the active layer is formed, and the length of the region is different between the two resonators so that the active layer And a semiconductor laser device having different lengths in the resonator direction of a region into which current is injected. The semiconductor laser device according to claim 4, wherein a band gap energy of a semiconductor layer in a region in which propagated light exists in a region where no current is injected into the active layer is larger than an energy of an active layer emission wavelength. The method of claim 1, wherein the two active layers each comprise (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 ≦ _y ≦ 1) and Al _z Ga _lz As (0 ≦ _z ≦ The semiconductor laser device comprised from the layer containing 1) and whose wavelengths obtained by two active layers are 630 nm or more and 690 nm or less, and 760 nm or more and 810 nm or less, respectively. 7. The semiconductor laser device according to claim 6, wherein the maximum light output of each of the single cross-sections obtained in the two active layers is 80 mW or more. 5. The method of claim 4, wherein the band gap of at least a portion of the quantum well active layer in one or both cross-sections of the at least one resonator facing the resonator center direction is enlarged by disordering the impurity diffusion or the impurity implantation, and the current is increased. The semiconductor is provided with a current blocking layer, or a portion of the semiconductor layer or electrode corresponding to the current injection path is removed, and the length from the end face in which the process is performed to the center of the resonator is different in two resonators. Laser device. The semiconductor laser device according to claim 1, wherein the maximum light output obtained in said active layer is different. 10. The method of claim 9, wherein the at least two active layers comprise at least two layers including (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 ≦ _y ≦ 1). The semiconductor laser device of which the light output in the element with the highest maximum light output among the active layers is 50 mW or more, and the operating current of the element with the lowest maximum light output is 35 mA or less at the light output of 2 mW or more. Forming a first laminated structure by sequentially laminating a first first conductive cladding layer, a first active layer, and a first second conductive cladding layer on the substrate; Removing the first laminated structure in a predetermined region on the substrate; Forming a second laminated structure by sequentially laminating a second first conductive clad layer, a second active layer, and a second second conductive clad layer on the substrate including the first laminated structure. Fair, Removing the second laminated structure formed on the first laminated structure; Forming a layer serving as an impurity diffusion source in a predetermined region on the first laminated structure and the second laminated structure; Heat-treating the substrate to diffuse impurities from the layer serving as the impurity diffusion source to the first stacked structure immediately below and the second stacked structure, so that at least one of the first active layer or the second active layer Including the process of disordering any part, A region in which the impurity is diffused in the first laminated structure and the region in which the impurity is diffused in the second laminated structure have different widths in the resonator direction. . 12. The method of manufacturing a semiconductor laser device according to claim 11, wherein a width in the resonator direction of the layer serving as the impurity diffusion source is different on the first laminated structure and on the second laminated structure. 12. The method of claim 11, wherein the length of the resonator in the region where the current of the first active layer is injected is different from the length of the resonator in the region where the current of the second active layer is injected. 12. The method of claim 11, wherein at least one of the first active layer or the second active layer is a quantum well structure. The method for manufacturing a semiconductor laser device according to claim 11, wherein the light emission wavelengths obtained in the first active layer and the second active layer are different from each other. Forming a laminated structure by sequentially laminating a first conductive type cladding layer, an active layer, and a second conductive type cladding layer on a substrate; Processing the second conductive cladding layer to form at least two or more ridge stripe structures arranged in parallel; Diffusing an impurity on the laminate structure including the at least two ridge stripe structures, thereby disordering a portion of the active layer immediately below the at least one ridge stripe structure; Wherein the region in which the impurities are diffused immediately below one of the ridge stripe structures and the region in which the impurities are diffused immediately below another ridge stripe structure have different widths in the resonator direction. Method of manufacturing the device. 17. The method of manufacturing a semiconductor laser device according to claim 16, wherein the length of the resonator direction is different in the gain region of the active layer immediately below the one ridge stripe structure and the gain region of the active layer directly below the other ridge stripe structure.